Fróðskaparrit - 01.01.1999, Page 227

ECHINODERMATA, ASTEROIDEA í FØROYSKUM ØKI
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plateau down to about 50 m depth. The
most common bottom types are sandy sedi-
ments and shell-sand bottoms mixed with
Modiolus modiolus. Modiolus bottom is
found predominantly in shallow water be-
tween the islands and on the plateau down
to about an 80 m depth. Between depths of
100 m and 300 m, sand is the dominant
sediment.
Klitgaard (1992) has analysed informa-
tion collected during the BioFar pro-
gramme, together with information from
local fishermen. East of Nolsøy, in an area
with MoJio/níshell-sand, a high concentra-
tion of living Modiolus modiolus is found
in depths of 60 to 100 m. Down to about
200 m, large areas with shell-sand are
found in the west and south-west parts of
the Faroes. Further down, sand sometimes
mixed with pebbles and stones is the domi-
nant bottom sediment. Both east and west
of the Faroes, a soft bottom area is found at
a depth of about 350 m. Part of the soft bot-
tom area found east of the islands is cov-
ered with a compact mat of sponge
spicules. Such mats are also found in other
areas down to a depth of about 900 m.
At the Faroe Bank, and probably also at
the Bill Baily and Lousy Banks, the domi-
nant sediment is fine, shell-sand. Coarse
shell remains are dominant in steep areas.
During the BioFar programme, the sedi-
ment brought on deck probably often gave
the impression of being a more coarse bot-
tom sediment than is probably the case.
Eleven hundred underwater pictures taken
at depths between 60 and 1,050 m on a
spring cruise (1990) by Dr. Julian Gutt, and
a hundred pictures taken at depths of 241 to
275 m by Dr. Hákan Westerberg at Suðuroy
Bank on a cruise (May/June 1989) all
showed mostly sandy sediments (Klit-
gaard, 1992).
Water Masses
Fossá et al. (1992) concluded that in an area
of complex hydrography, species may be
grouped and classified according to their
distribution in the water masses. Know-
ledge about water masses in the Faroe Is-
lands region may be important for zoogeo-
graphical analyses. According to Hansen
and Meincke (1979), Becker and Hansen
(1988), and Westerberg (1990), these areas
are, for the most part, dominated by three
main categories of water mass, which differ
with respect to formation area and general
flow direction: Atlantic Water (AW), bot-
tom water of the Norwegian Sea (NW), and
Arctic Intermediate Water (AI).
The warm and salty Atlantic Water (AW)
forms an inflow of water into the upper lay-
ers of the Norwegian Sea. The salinity is >
35.1 pss. The temperature is above 7°C, ex-
cept in depressions on the Faroe Plateau
where winter-cooled water might be trap-
ped.
The bottom water of the Norwegian Sea
(NW) forms the coldest component of the
water, overflowing the thresholds around
the Faroes into the Atlantic. The tempera-
ture is below 0°C and the salinity ca. 34.92
pss.
Between the warm AW and the cold NW,
Arctic Intermediate Water (AI), mixed with
North Icelandic Winter Water (NI), is pre-
sent. These water masses (here called only
AI) are formed north of the Arctic (or Po-